To add an email sign up to Lock Screen in Squarespace, you can follow these.
#1. Because you can’t add email signup in this area, so we will use a free tool to create email signup, then embed it to Lock Screen via Code Injection.
First, you need to create an email signup via this free tool.
Choose a desired layout and choose Continue with this template
#2. You can add more fields, customize newsletter signup, then click Add to website for free
#3. Click Publish on top right of website
#4. Choose Free Plan and Copy Embed code
#5. Click Pages
Scroll down and click Website Tools
Click Code Injection
#6. Scroll down to Lock Page > Paste embed code here
#7. Result
#8. When users enter their email, submissions will be sent to your email
#9. To change email, you can open free tool in #1 and click Email > Notify Me